The present invention relates to diaphragm pumping apparatus, and more particularly to a diaphragm pump of the submersible type wherein the diaphragm pumping chamber is remotely positioned from its hydraulic driving element.
Submersible pumps have considerable utility in the art of pumping, chiefly because they are self-priming and more efficient than suction feed pumps, and can be actuated to provide immediate delivery of the liquid in which they are immersed. Continuous immersion of the pump in the liquid eliminates the need for periodic cleaning of the pump components, for so long as the liquid level is maintained above the elevation of the pump the effects of air drying are eliminated. These features have particular application and utility in the field of paint spray painting, particularly when painting from containers having predetermined volumes of paint. For example, paint is commercially available in one gallon and five gallon containers, and it is advantageous to provide a pumping apparatus which is conveniently adaptable to containers of these sizes for applying the liquid contained therein.
U.S. Pat. No. 3,317,141, issued May 2, 1967, shows an airless spray gun coupled to a tubular diaphragm paint pump immersed in a container of paint, wherein the tubular diaphragm is alternately contracted and expanded by the application of pressurized oil delivered from a reciprocating oil pump coupled to the outside walls of the tubular diaphragm, by means of a hose or tube intermediate the diaphragm pump and the reciprocating oil pump. This pump has a disadvantage in that it requires manual priming under certain conditions of operation, and further in that it utilizes a relatively complex construction to accomplish the pumping operation.
U.S. Pat. No. 3,623,661, issued Nov. 30, 1971, shows another form of diaphragm pump which is itself not immersed in the liquid, but is connected via an elongated tube to a filter which is immersed in the liquid. This device also suffers from the disadvantage that it requires a bypass flow connection for priming the pump, thereby requiring certain preliminary steps to be taken before pumping can be accomplished with the system.
U.S. Pat. No. 3,788,554, issued Jan. 29, 1974, shows a diaphragm pump which is immersed into a liquid container wherein the diaphragm is driven by a hydraulic oil column coupled through an elongated tube to one side of the diaphragm, the other end of the tube being coupled into a reciprocating piston chamber. The piston develops a reciprocating pressure pulse in the hydraulic oil in the tube which causes the diaphragm to move in correspondence and thereby to pump liquid from the container. Air entrainment in the hydraulic oil of the tube, or a tube of excessive length or volume, can cause this pump to operate inefficiently or even to become inoperative, if the reciprocating pulses developed by the piston into the oil are absorbed into the air and are not readily transmitted to the diaphragm pumping chamber.
There is a need for a submersible diaphragm pump which can efficiently pump liquids from a container to minimize the problem of air entrainment in the hydraulic driving oil and irrespective of the length or volume of the tubular column of hydraulic oil which extends between the diaphragm pump and the driving piston mechanism. The present invention meets this need according to the teachings which will become apparent from the specification and claims.